Vitamins for Hair Growth: What Actually Works

Hair supplements are a billion-pound industry — but which ingredients have actual evidence?

The global hair supplement market is worth over a billion pounds and growing. Scroll through any social media feed and you will see influencers promoting gummies, capsules, and powders that promise thicker, stronger, shinier hair. The marketing is confident. The evidence, in many cases, is not.

The reality is more nuanced. Under EU Regulation 432/2012 (retained in UK law post-Brexit), only three nutrients hold authorised health claims specifically for hair. A handful of others have clinical data linking deficiency to hair loss, even without an authorised claim. And some of the most heavily marketed ingredients have very little evidence at all.

This article covers what the research actually says — which nutrients have regulatory approval for hair claims, which have clinical evidence worth paying attention to, and which are largely marketing.

Which nutrients have EU-authorised claims for hair?

Under EU Regulation 432/2012, only three nutrients are permitted to claim they contribute to the "maintenance of normal hair." These are:

Biotin — contributes to the maintenance of normal hair
Zinc — contributes to the maintenance of normal hair
Selenium — contributes to the maintenance of normal hair

That is the complete list. No other nutrient — not iron, not vitamin D, not collagen, not keratin — holds an authorised health claim for hair under current UK and EU food law.

This does not mean other nutrients are irrelevant to hair health. It means the regulatory bar for an authorised claim is high, and the European Food Safety Authority (EFSA) has not approved claims for every nutrient with clinical evidence. Several nutrients without authorised hair claims have strong data linking their deficiency to hair loss.

Biotin — the most marketed hair vitamin

Biotin (vitamin B7) is the ingredient most commonly associated with hair supplements. It carries the authorised claim that it "contributes to the maintenance of normal hair," and it appears in virtually every hair supplement on the market.

However, there is an important distinction between an authorised maintenance claim and evidence that supplementation will make hair grow faster, thicker, or stronger in people who are not deficient.

A systematic review by Patel, Swink, and Castelo-Soccio (2017) examined the published literature on biotin for hair loss and concluded that evidence supporting biotin supplementation is limited to cases of biotin deficiency. In individuals with adequate biotin status — which is the vast majority of the population, since biotin deficiency is rare — there is insufficient evidence that additional biotin produces meaningful improvements in hair growth or quality.

Biotin deficiency does exist, particularly in people with certain genetic conditions, those taking specific medications (such as anticonvulsants), or those with very restricted diets. In these cases, supplementation is clearly warranted. But for the general population, biotin is unlikely to be the missing piece.

PARTICULAR includes biotin in its formulation at a dose calibrated through the questionnaire, because the authorised claim is valid and because certain dietary patterns and life stages do increase the risk of suboptimal status. The honest position is that biotin matters — but it is not the transformative ingredient the marketing would have you believe.

Zinc — authorised claim with stronger deficiency evidence

Zinc carries the same authorised claim as biotin — it "contributes to the maintenance of normal hair" — but the clinical evidence linking zinc deficiency to hair loss is more robust.

A study by Kil, Kim, and Kim (2013) analysed serum zinc concentrations in patients with various types of hair loss (alopecia areata, male and female pattern hair loss, and telogen effluvium) and found that mean serum zinc was significantly lower in all hair loss groups compared to controls. The authors concluded that zinc metabolism disturbances play a key role in hair loss, particularly in alopecia areata and telogen effluvium.

Zinc is involved in protein synthesis, cell division, and immune function — all of which are relevant to the hair follicle cycle. The hair follicle is one of the most rapidly dividing cell populations in the body, making it particularly sensitive to nutritional deficiencies.

Groups at higher risk of low zinc status include vegans and vegetarians (due to phytate-mediated inhibition of zinc absorption from plant foods), older adults, and people with gastrointestinal conditions affecting absorption.

Selenium — authorised claim, but dose matters

Selenium is the third and final nutrient with an authorised claim for hair — it "contributes to the maintenance of normal hair." But selenium is a nutrient where the therapeutic window is unusually narrow, and this is directly relevant to hair.

At adequate intakes, selenium contributes to normal hair maintenance. At excessive intakes, selenium can cause the opposite — hair loss is a hallmark symptom of selenosis (selenium toxicity). A case report by Senthilkumaran et al. (2012) documented acute alopecia resulting from excessive selenium intake through over-consumption of selenium-rich Brazil nuts used as a nutritional therapy.

The UK Reference Nutrient Intake (RNI) for selenium is 75 micrograms per day for men and 60 micrograms per day for women. The Scientific Committee on Food set an upper tolerable intake of 300 micrograms per day for adults, but symptoms of toxicity have been reported at chronic intakes well below that threshold.

This is why dose calibration matters. A supplement that includes selenium for its authorised hair claim must get the amount right — enough to support maintenance of normal hair, not so much that it contributes to the very problem it claims to address. PARTICULAR adjusts selenium dose through the questionnaire based on dietary intake and other factors.

Iron — no authorised hair claim, but strong clinical evidence

Iron does not carry an authorised health claim for hair. Under EU Regulation 432/2012, its authorised claims relate to the normal formation of red blood cells and haemoglobin, normal oxygen transport, the reduction of tiredness and fatigue, and normal cognitive function.

Despite the absence of a hair-specific claim, iron deficiency is one of the most well-documented nutritional causes of hair shedding, particularly in women.

Trost, Bergfeld, and Calogeras (2006) conducted a comprehensive review of the relationship between iron deficiency and hair loss, noting that multiple studies have found associations between iron deficiency and alopecia areata, androgenetic alopecia, telogen effluvium, and diffuse hair loss.

Olsen et al. (2010) investigated iron deficiency specifically in women with female pattern hair loss and chronic telogen effluvium, comparing serum ferritin levels against control groups without hair loss. The study, conducted at Duke University Medical Center, provided further evidence for the clinical association between low iron status and hair shedding in women.

Iron deficiency is the most common nutritional deficiency in the UK. According to the National Diet and Nutrition Survey, 25% of women aged 19–64 have iron intakes below the Lower Reference Nutrient Intake — the level below which deficiency is likely. Women who menstruate, follow plant-based diets, or both are at greatest risk.

The takeaway: iron does not have an authorised hair claim, but if your hair is shedding and your iron status is low, addressing the deficiency is one of the most evidence-based interventions available.

Vitamin D — no authorised hair claim, but observational data

Vitamin D does not carry an authorised health claim for hair. Its authorised claims relate to the normal function of the immune system, maintenance of normal bones, normal muscle function, and normal absorption of calcium and phosphorus.

However, observational studies have consistently found an association between low vitamin D status and hair loss. A systematic review and meta-analysis by Tsai and Huang (2018) found that patients with alopecia areata had significantly lower serum 25-hydroxyvitamin D concentrations compared to healthy controls.

It is important to note that these are observational findings — they demonstrate an association, not a causal relationship. It is not yet established from randomised controlled trials that correcting low vitamin D status will reverse hair loss. However, given the widespread prevalence of vitamin D insufficiency in the UK — the Scientific Advisory Committee on Nutrition recommends all UK adults consider supplementation, particularly from October to March — ensuring adequate vitamin D status is sensible for general health, regardless of any potential hair benefit.

MSM — emerging evidence, no authorised claim

MSM (methylsulfonylmethane) is a naturally occurring sulfur compound. It does not hold an EU-authorised health claim for hair, and the evidence base is smaller than for the nutrients discussed above. But the preliminary data is worth examining honestly.

Sulfur is a structural component of keratin — the protein that makes up hair, skin, and nails. MSM provides bioavailable sulfur, which is the biological rationale for its inclusion in hair and skin formulations.

An animal study by Hummadi, Gany, and Hadi (2022) evaluated topical MSM alone and in combination with minoxidil in mice, finding that MSM reduced hair loss through antioxidant and anti-inflammatory mechanisms. A human study by Muizzuddin and Benjamin (2022) found that oral MSM supplementation at doses of 1g and 3g per day reduced visible signs of skin ageing, though this study measured skin rather than hair outcomes.

The honest assessment: the mechanistic rationale for MSM and hair is sound (sulfur is essential for keratin structure), early data is promising, but large-scale human trials specifically measuring hair outcomes are still lacking. This is a nutrient to watch, not one to make bold claims about.

What about collagen, keratin, and "hair gummies"?

Three categories of hair supplements deserve a brief, honest evaluation.

Collagen

Collagen is one of the most marketed hair and skin supplements. It does not hold an authorised health claim for hair. The majority of collagen supplements are derived from bovine or marine sources, meaning they are not vegan. PARTICULAR does not include collagen because it is an animal-derived ingredient, and because the evidence for oral collagen supplementation specifically improving hair growth is limited. Your body breaks down ingested collagen into amino acids — it does not direct those amino acids preferentially to your hair follicles.

Keratin

Keratin supplements are marketed on the basis that hair is made of keratin, so consuming keratin should help hair. This logic is simplistic. Like collagen, ingested keratin is broken down into its constituent amino acids during digestion. There is minimal clinical evidence that oral keratin supplementation produces meaningful improvements in hair growth in people with adequate protein intake.

Hair gummies

Sugar-loaded gummy vitamins have become the dominant format in the hair supplement category, driven primarily by social media marketing. Many contain added sugars, artificial colours, and flavourings while delivering underdosed active ingredients. The gummy format limits how much of each nutrient can be included per serving, and the high-sugar matrix can compromise the stability of certain vitamins. If a product tastes like a sweet, it is probably more sweet than supplement.

Why personalisation matters for hair health

Hair health is systemic. Hair follicles are among the most metabolically active structures in the body, and they are sensitive to nutritional status, hormonal balance, stress, and overall health.

This means the "best vitamin for hair growth" depends entirely on what your body actually needs. A woman experiencing hair shedding due to iron deficiency needs iron, not more biotin. Someone with low zinc status needs zinc. A person with adequate levels of everything may not benefit from any hair supplement at all.

Generic hair supplements take a one-size-fits-all approach — the same formula regardless of your diet, your deficiency risk, or your life stage. PARTICULAR takes a different approach. The questionnaire captures the factors that affect your individual nutrient requirements — dietary patterns, menstrual status, lifestyle, and health goals — and builds a personalised formula delivered as loose microgranules in a daily scoop.

Each nutrient is contained in its own individually coated granule, avoiding the competitive absorption issues that occur when minerals like iron, zinc, and calcium are compressed together in a single tablet. Your formula includes the nutrients you are most likely to need, at doses calibrated to your individual profile.

Key takeaways

Only three nutrients hold EU-authorised claims for "maintenance of normal hair": biotin, zinc, and selenium
Biotin has the authorised claim, but evidence for supplementation in non-deficient individuals is limited — deficiency is rare in the general population
Zinc deficiency is significantly associated with multiple types of hair loss, and groups including vegans and vegetarians are at higher risk of low status
Selenium has the authorised claim, but the dose must be carefully calibrated — excessive selenium intake can itself cause hair loss
Iron has no authorised hair claim, but iron deficiency is one of the most common and well-documented causes of hair shedding in women
Vitamin D has no authorised hair claim, but low vitamin D status is consistently associated with alopecia areata in observational studies
MSM has no authorised claim and limited clinical data, but the mechanistic rationale (bioavailable sulfur for keratin synthesis) is sound and early research is promising
The "best vitamin for hair growth" depends on what your body actually needs — a personalised approach based on individual risk factors is more rational than a generic formula
PARTICULAR builds your formula through a questionnaire, delivering personalised doses in individually coated microgranules — one daily scoop from a pouch, not capsules or tablets

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